This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-126104, filed May 6, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a substrate processing apparatus for applying a series of photolithography process to a substrate such as a semiconductor wafer or a glass substrate for a liquid crystal display device.
A coating-developing system (substrate processing apparatus) disclosed in, for example, U.S. Pat. No. 5,664,254 is used performing a photolithography process applied to a semiconductor device. The developing station included in this system comprises a Chill-Hot-Plate (CHP) unit for Post-Exposure Baking (PEB) a chemically amplified resist film exposed to light in a pattern. The CHP unit includes a hot plate mechanism for heating a wafer, a cooled plate mechanism for cooling the wafer, and a transfer mechanism for transferring the wafer between the hot plat mechanism and the cooled plate mechanism and serves to prevent over-baking of the resist film. To be more specific, the wafer immediately after heated by the hot plate mechanism is transferred to the cooled plate mechanism so as to be cooled promptly to room temperature. As a result, the PEB time is controlled highly accurately so as to prevent effectively the resist film from being over-baked. It follows that a desired resolution can be obtained in the subsequent developing treatment.
In the conventional CHP unit, however, the hot plate mechanism is arranged in the vicinity of the wafer inlet-outlet port, and the cooled plate mechanism is arranged away from the wafer inlet-outlet port and behind the hot plate mechanism relative to the water inlet-outlet port, with the result that the cooled wafer W receives radiation heat from the hot plate when the wafer W is taken out of the CHP unit through the wafer inlet-outlet port. To be more specific, when the cooled wafer W is taken out of the CHP unit through the wafer inlet-outlet port, the wafer W is moved above the hot plate so as to receives radiation heat from the hot plate, resulting in wafer temperature elevation. It follows that it is difficult to maintain highly accurately the temperature of the wafer W delivered to the developing unit.
It should also be noted that, in the conventional apparatus, a plurality of CHP units are stacked one upon the other to form multi-stages, with the result that nonuniformity of temperature is brought about among the wafers processed by the CHP units. On the other hand, since the developing unit to which the wafer taken out of the CHP unit is to be transferred is not determined, the wafer is transferred into a vacant developing unit that is not being used. In other words, wafers of various temperatures are introduced into the developing unit, giving rise to nonuniformity among the wafers in the resolution. If the wafers before the developing treatment are nonuniform in temperature, the developing treatments of the wafers are rendered nonuniform, leading to a low yield.
An object of the present invention is to provide a substrate processing apparatus and a substrate processing method that permit suppressing the nonuniformity in temperature of the substrates before the developing treatment so as to obtain a high yield.
It is conceivable to mount a cooling plate that permits the temperature control with a high precision to each CHP unit in order to prevent nonuniformity in the wafer temperature among the CHP units. However, such a cooling plate is costly, leading to a high apparatus cost. Also, since a hot plate adapted in size to have the wafer mounted thereon, a cooling plate and a transfer mechanism are mounted to the CHP unit, the apparatus is rendered bulky and heavy if a control apparatus for a high precision temperature control is further mounted to the apparatus.
Under the circumstances, the present inventors have conducted extensive research on the parallel PEB processing of a large number of wafers, arriving at the present invention.
According to a first aspect of the present invention, there is provided a substrate processing apparatus for processing a substrate by a photolithography process, comprising:
a plurality of heating sections for heating substrates, respectively;
a plurality of first cooling sections, the number of which is equal to or smaller than the number of the heating sections, for cooling the substrate heated in the heating section to a first temperature;
a second cooling section for further cooling the substrate cooled in the first cooling section to a second temperature lower than the first temperature; and
a plurality of liquid process sections for supplying a process liquid to the substrate cooled in the second cooling section to form a liquid film of the process liquid on the substrate.
According to the first aspect of the present invention, the substrate after heating is preliminarily cooled in the first cooling section, followed by further cooling the substrate to the second temperature, making it possible to control the substrate temperature with high precision. As a result, it is possible to suppress the nonuniformity of processing, which is caused by the substrate temperature, in the substrate process section, leading to a high yield.
It is possible for the substrate processing apparatus of the present invention to further comprise a first transfer mechanism for transferring the substrate between the heating section and the first cooling section and a second transfer mechanism for transferring the substrate between the first cooling section and the second cooling section. In this case, the heating time in the heating section can be controlled by the first substrate transfer means.
It is desirable for the liquid process section to comprise a developing section for forming a liquid film of the developing solution on the substrate, and each of the first and second cooling sections should desirably be arranged between the developing section and the heating section. In this case, the developing section is unlikely to be thermally affected by the heating section, making it possible to achieve a developing treatment with high precision.
The second cooling section may be positioned so as to be surrounded by the plurality of liquid process sections such that the cooled substrate may be supplied to each of these liquid process sections. In this case, nonuniformity in the cooling of the substrate does not take place in the second cooling section, leading to a high uniformity of processing.
The second cooling section may be arranged in the vicinity of only one of the plurality of liquid process sections such that the cooled substrate may be supplied to only the liquid process section positioned adjacent to the second cooling section. In this case, even if nonuniformity of the cooling temperature is generated among the plurality of second cooling sections, a liquid film of the process liquid can be formed on the substrate under the conditions conforming with the cooling temperature in the second cooling section, leading to a uniform processing.
It is desirable for the apparatus of the present invention to comprise a third transfer mechanism for transferring the substrate between the second cooling section and the liquid process section. In this case, the second transfer mechanism also serves to transfer the substrate between the second cooling section and the liquid process section.
It is desirable for the liquid process section to comprise a resist coating section for coating a substrate with a resist solution and for the second cooling section to be arranged in the vicinity of the resist coating section.
Further, it is desirable for the apparatus of the present invention to comprise air conditioning means for making the second cooling section and the liquid process section substantially equal to each other in the atmosphere.
According to a second aspect of the present invention, there is provided a substrate processing method for processing the substrate by the use of photolithography process, comprising the steps of:
(a) transferring a substrate into a selected one of a plurality of heating sections for heating the substrate;
(b) transferring the substrate heated in the heating section in the step (a) into a selected one of a plurality of first cooling sections, the number of which is smaller than or equal to the number of the heating sections, for cooling the substrate to a first temperature;
(c) transferring the substrate cooled in the step (b) into a second cooling section for cooling the substrate to a second temperature lower than the first temperature; and
(d) transferring the substrate cooled in the step (c) to a liquid process section for forming a liquid film of a process liquid on the substrate.
It is possible to select one of a plurality of liquid process sections in step (d) for transferring the substrate from the second cooling section into the selected liquid process section. On the other hand, it is also possible to transfer in step (d) the substrate from the second cooling section into a specified liquid process section.
It is desirable to set the first temperature at about 40xc2x0 C. and the second temperature at about 23xc2x0 C.
It is desirable to supply in the step (d) a developing solution onto the substrate under an atmosphere substantially free from an alkali component.
Further, it is desirable to coat the substrate in the step (d) with a chemically amplified resist under an atmosphere substantially free from an alkali component.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.